stability of pH calibration fluid

[Capt_Cully]

I've got bottles of the high and low pH calibration fluid. They've got to be 6 or 7 years old. Is this stuff relatively stable and therefore trustworthy? Or is it the opposite, and should be replaced with new controls?

Thanks

 

[iamwrasseman]

usually there is an expiration date on something that has that sort of issue but the cheaper test kits are usually good for a year and then they start faltering and they have no expiration date .with that being said i would try to contact the manufacturer and see if they can lead you in the right direction but you know they will want to sell you new product and will probably tell you to order new calibration fluid .

 

[Johnny C]

IMHO- spend the few bucks for new ones. You can find one-time use packets for $1-2/ea. at the LFS and with all of the variables of a new setup it's worth it for the peace of mind.

 

[Capt_Cully]

Something I could have searched, but its a practice we should be doing regularly, so I thought someone might know off hand. If not, it was worth bringing it to the forefront for some attention, as pH.probes can drift over time.

Per my search, the esteemed Randy Holmes-Farley says they do drift slowly over time as CO2 interacts with the solution(paraphrasing). So I'm going with your responses Dave and JC. Its worth it to invest in new controls. However, the old stuff can still be used, but not trusted at its purchased control #.

 

[der_wille_zur_macht]

If you have significant quantities left, I would keep it - test it against a known good standard, note the date and the difference (if any), and adjust your calibration appropriately.

 

[pascal32]

No one locally has the packets. If you are in the Liverpool area sometime this weekend you can have a pack of 7 and 10 to calibrate with. I have extras that aren't expired